Human Evolution @ UCL


Bayesian Statistical Analysis dates Homo naledi to 912,000 years of age

13 June 2016

Homo naledi is a recently discovered species of fossil hominin from South Africa.

The Remains of Homo naledi A considerable amount is already known about H. naledi but some important questions remain unanswered. Here a team of scientists report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" They used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, they performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then they employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, they carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (HomoAu. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectusHomo habilisHomo floresiensisHomo sapiens, andAu. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. The team's findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed.

The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods

Mana Dembo, Davorka Radovcic, Heather M. Garvin, Myra F. Laird, Lauren Schroeder, Jill E. Scott, Juliet Brophy, Rebecca R. Ackermann, Chares M. Musiba, Darryl J. de Ruiter, Arne Mooers, Mark Collard

DOI: 10.1016/j.jhevol.2016.04.008